<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    
</body>
<script>
    //截取前五个字符，后面内容用······代替
    var text = "这是帖子5，主要内容是";
    var preview = text.slice(0,5);
    document.write(preview+"······");
</script>
</html>